Like you said, I think you want ashift=12.
If you're not going to use the extra space for something else, just give
all three whole disks to ZFS. Then later, you can replace the 1 TB disk
with a 2 TB disk and immediately double the usable space.
Or, since you're only going to get 2 TB of usable space out of this for
now, why not just mirror the 2 TB drives and forget about the 1 TB disk?
--
Richard
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